1. Field of the Invention
The present invention relates to a liquid crystal panel production technology, and in particular to a switch transistor and an equipment for etching the same.
2. The Related Arts
In the production of the thin film transistor (TFT), 5 times lithography process, which compares with 7 times lithography process, has shorter production cycle and higher yield, which can reduce the exposing number of forming TFT array. Therefore, in the present production of TFT-LCD, 5 times lithography process is usually used to prepare the TFT. 5 times lithography process generally comprises back channel etching TFT and etch stop TFT, wherein the process of the back channel etching TFT is simpler than that of the etch stop TFT and more suitable for mass production.
Referring to FIG. 1, in the process of the back channel etching TFT, after sequentially forming a gate 2, an insulation layer 3, an a-Si layer 4, an n+ a-Si layer 5, and a source/drain metal layer 6 of the TFT on a glass substrate 1, etch the a-Si layer 4 and the n+ a-Si layer 5 to form a channel 7 of the TFT.
Wherein, one step etching method is used in etching process of the channel 7 of the TFT. By using the same gas flow, the same power and the same pressure, the a-Si layer 4 and the n+ a-Si layer 5 are etched in one step. Moreover, the same parameters are used while over etching, so that the etching energy in the etching process of the channel 7 is too powerful. Therefore, the channel 7 will be bombarded by dry etching plasma, and the a-Si layer 4 is easy to be destroyed, leading to the poor electrical properties of the TFT. Secondly, the channel 7 is exposed outermost after the channel 7 is formed, so that the channel 7 will be bombarded by the plasma from chemical vapor deposition (CVD) in the process of forming silicon nitride, further leading to the poorer electrical properties of the TFT.